The pharmacological role of the kidney.

Renal function can modify the relationship between drug dose and clinical effect in a variety of ways. Effects on absorption, distribution volume and elimination influence the concentration of drug attained in blood. Consequently, such effects can often be detected and/or prevented by monitoring of serum concentrations of drugs. However, such monitoring alone is insufficient for optimum therapeutic use of drugs and must be accompanied by clinical monitoring of endpoints of efficacy and toxicity, since the relationship between the concentration of drug in serum and response may also be changed. Accumulation of active metabolites that are not measured by conventional drug assays makes interpretation of serum concentrations of drugs such as procainamide particularly hazardous. Effects of renal function on the relationship between amounts of drug in blood and response can only be detected by assessing endpoints of pharmacological effect. Since renal function can affect drug disposition by such a wide variety of mechanisms, the astute clinician must be aware of these potential mechanisms to make best use of his clinical skills and laboratory armamentarium for the benefit of his patients.